linux-kernel - RFC: Unneeded memory barriers

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Message-ID: <20061201141130.GA24203@linux-mips.org>
Date:	Fri, 1 Dec 2006 14:11:30 +0000
From:	Ralf Baechle <ralf@...ux-mips.org>
To:	linux-kernel@...r.kernel.org
Subject: RFC: Unneeded memory barriers

When disassembling a kernel I found around over 90 sync Instructions from
mb, rmb and wmb calls in the kernel and only few of those make any sense
to me.  So here's the first one - I think the wmb() in kernel/futex.c is
not needed on uniprocessors so should become an smb_wmb().

  Ralf

Signed-off-by: Ralf Baechle <ralf@...ux-mips.org>

diff --git a/kernel/futex.c b/kernel/futex.c
index 93ef30b..d867899 100644
--- a/kernel/futex.c
+++ b/kernel/futex.c
@@ -553,7 +553,7 @@ static void wake_futex(struct futex_q *q
 	 * at the end of wake_up_all() does not prevent this store from
 	 * moving.
 	 */
-	wmb();
+	smp_wmb();
 	q->lock_ptr = NULL;
 }
 
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